High frequency low noise twt helix fabrication



March 1, 1966 R. s. GORMLEY ETAL HIGH FREQUENCY LOW NOISE TWT HELIX FABRICATION i x V Filed Feb. 26, 1963 INVENTORS QBERT S. GORMLEY BY EUGENEHREZYEA ROY C. THOA/IAS United States Patent 3,237,285 HIGH FREQUENCY LOW NOISE TW'I HELIX FABRICATION Robert Stewart Gormley, West Long Branch, Eugene Henry Relyea, Neptune, and Roy Condit Thomas, Sea Bright, N.J., assignors to The Bendix Corporation, Eatontown, NJ., a corporation of Delaware Filed Feb. 26, 1%3, Ser. No. 261,161 4 Claims. (Cl. 29-155.5)

The present invention relates to electron discharge devices and more particularly to a method of fabricating a helix for a device of the traveling wave type. It is particularly applicable but not limited to the case in which the helix is supported by a thin wall vitreous tube such as glass to minimize the RF coupling loss to helical or cavity couplers and where the helix is to be plated to reduce its transmission loss.

In microwave electron discharge devices of the traveling wave type, a helix is used for the slow wave circuit. It is necessary that the helix be precisely dimensioned and the dimensions are not altered in the process of fabricating the device. This becomes exceedingly diflicult especially at the higher frequencies where the diameter of the helix and the wire becomes very small While the helix TPI becomes correspondingly large. Helix antenna dimension control and fabrication problems also become an increasing problem. Heretofore the helix was wound on a mandrel and the antennas fashioned to the end turns. The mandrel was then removed. This did not leave any support for the helix and antenna assembly when it was being inserted in a precision glass envelope. Thus the assembly would be altered as either the TPI was changed or the geometric control of the antenna was lost. This caused the electrical characteristics to be adversely affected.

The present invention provides a novel method for assembling the device. The helix is wound on precision OD nickel tubing in which a stiffening rod has been inserted. The helix antennas, if required, are precisely positioned on the tubing and welded to the helix. These antennas can easily be made as integral parts of helix anchoring collars. The above assembly is then fired. The rod is re moved and the helix inserted in the envelope. The nickel tubing is etched out. The helix and anchoring collar spring back will firmly anchor the helix assembly in position in the envelope. The firing temperature may be adjusted so each turn of the helix will contact the glass envelope but no excess tension will cause TPI distortion.

It is an object of the invention to provide an improved process for fabricating an electron discharge device.

Another object of the invention is to provide an improved method of fabricating a helix for an electron discharge device.

Another object of the invention is to provide an im proved method for assembling a helix in a glass envelope.

The above and other objects and features of the invention will appear more fully hereinafter from a consideration of the following description taken in connection with the accompanying drawing wherein one embodiment of the invention is illustrated by way of example.

In the drawing:

FIGURE 1 is a cutaway view of a helix and mandrel assembly.

FIGURE 2 is a view of the assembly of FIGURE 1 with the stiffening rod removed.

FIGURE 3 shows the helix of FIGURE 1 installed in a glass envelope.

Referring now to the drawing, a helix 1 is shown wound on a tubing 2 in which a stiffening rod 3 has been inserted. The helix 1 may be wound from a copper plated tungsten or molybdenum wire. In order to form the small size helix necessary for the very high microwave frequencies, the wire is heated so that it will not crack when wound on such a small radius.

The tubing 2 may be of nickel and has a precision outside diameter and a relatively thin wall. As the tubing 2 does not have sufficient strength to prevent deformation when the helix l is wound under tension, it is necessary to insert the stiffening rod 3 for reinforcement. Collars 4 and 5 are located on the tubing 3 and are connected to the helix 1 by antennas 6- and 7 by welding or other suitable manner.

After th ecollars 4 and 5 are secured to the helix 1 by the antennas 6 and 7 and the assembly fired, the stiffening rod 3 may be removed. Normally the stiffening rod 3 can be removed without too much difficulty. If necessary, it can be stretched to reduce the diameter. The tubing 2 protects the helix 1 from deformation while the rod 3 is being removed.

Next the helix 1 on the tubing 2 is inserted in the tubulation section 8 of an envelope, see FIGURE 3, and precisely located at the predetermined distance from the gun section of the envelope (not shown). The aforenoted assembly is then placed in a nickel stripping solution until the nickel tubing has been dissolved. As an example, the assembly was placed in a container of boiling Niplex, which is a nickel stripping solution manufactured by Hanson Van Winkle Mining Company. The assembly was kept in the heated solution until the nickel tubing had been removed. The copper plating is not affected by this solution.

It is understood that in the drawing, the assembly is illustrated on quite an enlarged scale. In a typical example, the diameter of the helix would be approximately one sixteenth of an inch and a length of around seven inches. The helix would have at least turns to the inch. Thus it can be seen that the process described heretofore will facilitate the fabrication of the device.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangement of the parts, which will now appear to those skilled in the art, may be made Without departing from the scope of the invention.

What is claimed is:

1. A method of fabricating a helix for an electron discharge device comprising inserting a stiffening rod in a nickel tube, winding a helix on said tube, attaching an tennas to said helix, removing said stiffening rod, inserting said helix and antennas assembly into an envelope, and dissolving out said nickel tube.

2. A method for fabricating a helix for a traveling wave type electron discharge device, comprising winding a helix on a nickel tubing which has a stiffening rod inserted therein, attaching connections to said helix, removing the stiffening rod from said tubing, inserting the helix assembly into a glass tubing, and etching out the nickel tubing.

3. A method of fabricating a helix structure for an electron discharge device, comprising placing a stifiening References Cited by the Examiner rod in a thin nickel tubing, Winding a wire around said UNITED STATES PATENTS tubing to form a helix, fastening collars and antennas to both ends of said helix, removing said stiffening rod, in- 2,067,746 1/1937 Zabel g setting said helix and nickel tubing in an envelope, and 5 11/1957 Robertson placing said envelope in a hot nickel strippin solution to dissolve Said nick e1 tubing WHITMORE A. WILTZ, Przmmy Excnmmer.

4. The method as set forth in claim 3 in which said RICHARD H. EANES, W. I. BROOKS, wire is heated While being Wound. Assistant Examiners. 

1. A METHOD OF FABRICATING A HELIX FOR AN ELECTRON DISCHARGE DEVICE COMPRISING INSERTING A STIFFENING ROD IN A NICKEL TUBE, WINDING A HELIX ON SAID TUBE, ATTACHING ANTENNAS TO SAID HELIX, REMOVING SAID STIFFENING ROD, INSERTING SAID HELIX AND ANTENNAS ASSEMBLY INTO AN ENVELOPE, AND DISSOLVING OUT SAID NICKEL TUBE. 